The long range goal of the proposed research is to gain insight into the mechanisms of signal transduction in the photoreceptor cells of the visual system. It is anticipated that the results obtained from this study will aid in understanding the basis of sensory reception and information processing in the nervous system. The immediate goal of this pilot research projects is to a develope system in which isolated photoreceptor neurons of Drosphila can be identified and maintained in cell culture for the purpose of the electrophysiological characterization of the light activated currents. Cell cultures of isolated photoreceptors will be prepared by enzymatic and mechanical dissociation of embryonic,larval, pupal and adult eye tissue. The identity of photoreceptor cells in the cultures will be determined by using fluorescently labeled photoreceptor cell specific monoclonal antibodies. In parallel experiments aimed at identifying the photoreceptor cells, Fura-2, a fluorescent Ca++ concentration indicator, will be used to detect light activated intracellular Ca++ transients which are likely to be absent from the other cell types in the cultures. Patch clamp recording techniques will be used to study the biophysical properties of light activated ion channels in attached and excised membrane patches. The aim of this analysis will be to identify the Intracellular messenger which directly activates the light sensitive channels in the invertebrate preparation.